What Does 305/30R15 Actually Mean?

Let's break it down simply: The 305 means this tire has a tread width of 305 millimeters. The 30 is the aspect ratio, which means the sidewall height is 30% of that width. The "R" stands for Radial construction (the modern standard for safety and durability), and finally, the 15 indicates that this tire perfectly fits a 15-inch wheel.